The present invention relates generally to the field of window coverings, and more particularly, to a light control window covering and a method and apparatus for its manufacture.
Light control window coverings typically include a front and rear portion made from a sheer material and a plurality of opaque vanes extending between the sheer material. The light control covering is movable from an open, light-passing position in which the vanes are horizontal, to a light-blocking position in which the vanes are substantially vertical.
Numerous methods have been developed to form light control window coverings. U.S. Pat. No. 3,384,519 to Froget discloses a method of welding the marginal edges of a plurality of vanes to two layers of material. First, each vane is welded to one face of the first layer of material. As each vane is welded to the first layer of material, the first layer and the welded vane are wound onto a reel. After all of the vanes have been welded to the first layer of material and wound onto a reel, the combination is then unwound such that the free edge of each vane comes into contact with a second layer of material. The free edge is then welded to the second layer of material. In this manner a light-control window covering is formed with one face of the vane being welded at its marginal edge to the first layer and the second face of the vane being welded at its second marginal edge to the second layer.
U.S. Pat. No. 5,313,999 to Colson et al. describes a method and apparatus for forming a light-control window covering, in which one side of individual vanes are attached with adhesive to a first continuous sheet of material and the other side of the vanes are then attached with adhesive to a second continuous sheet of material. The first and second sides of each vane are attached to the first and second sheets in a continuous line. Both the Froget and Colson patents require that the vanes be attached to the first and second sheets individually, one at a time.
U.S. Pat. No. 5,228,936 to Goodhue, describes a method and apparatus for forming a light-control window covering, in which all of the vanes are attached with adhesive to the first and second sheets simultaneously. As in Froget and Colson, one side of each vane is attached to a first sheet and the other side of each vane is attached to a second sheet. Since the vanes are applied to the first and second sheets side by side, the vanes do not overlap when the window covering is in the light-blocking position. As a result, light is likely to pass through the spaces between adjacent vanes.
U.S. Pat. No. 5,888,639 to Green et al. discloses a method and apparatus for forming a light-control window covering formed by continuously welding three substrates of material together to form a three-substrate web having first and second light-control regions and a center vane or opaque region located therebetween. Portions of the three-substrate web are laterally offset from one another and adhesively attached to from a light-control window covering.
U.S. Pat. Nos. 5,846,360; 5,885,409; and 5,891,208, to Gill, an inventor common to the instant application, disclose a method and apparatus for manufacturing a multilayer filter by attaching first and second filter layers to a plurality of ribbons utilizing ultrasonic welding equipment.
It would be desirable to form a light-control window covering in which all of the vanes are simultaneously attached to the first and second sheets where the vanes of the resultant light-control window covering overlap one another in the open or light-passing position.
One embodiment of this invention relates to a light-control window covering comprising a first sheet of sheer material, and a second sheet of sheer material spaced apart from the first sheet of sheer material. A plurality of vanes is ultrasonically welded to the first and second sheets of sheer material. Each vane includes a first face and a second face, a center region, and a first and a second longitudinal margin. The first face of each vane is ultrasonically welded to the first and second sheets of sheer material along the respective first and second longitudinal margins.
The vanes are movable from a light-passing position in which the center region of each vane is substantially perpendicular to the first and second sheets of sheer material, to a light-blocking position in which the center region of each vane is substantially parallel to the first and second sheets of -sheer material. The second longitudinal margin of each vane is folded over and adjacent the center region of each respective vane in the light-blocking position. The vanes are spaced from one another such that in the light-blocking position the first longitudinal margin of one vane overlaps the second longitudinal margin of an adjacent vane.
Another embodiment of this invention includes a method for manufacturing the light-control window covering comprising feeding along a path a first and a second sheet of sheer material spaced apart from and parallel to one another. Each sheet of sheer material has a longitudinal direction and a cross-wise direction perpendicular to the longitudinal direction. The method further includes feeding a plurality of strips of vane material. Each strip of vane material has a pair of longitudinal edges and a predetermined width as measured between the longitudinal edges, a center region, a first side and a second side, and first and second longitudinal margins. Each strip of vane material is separated from an adjacent strip of vane material by a predetermined distance that is less than the predetermined width of the strip of vane material. The strips of vane material are bonded to the first sheet of sheer material along the first longitudinal margin and to the second sheet of sheer material along the second longitudinal margin.
Still another embodiment includes an apparatus for manufacturing a light-control window covering having a first sheet of sheer material, a second sheet of sheer material and a plurality of vanes. The apparatus includes a plurality of folders spaced apart from one another for folding the longitudinal margins of the vanes. Additionally, the apparatus includes a plurality of first ultrasonic welders for welding a first longitudinal margin of each vane to the first sheet of sheer material, and a plurality of second ultrasonic welders for welding a second longitudinal margin of each vane to the second sheet of sheer material. A plurality of rotary anvils are located between the first and second sheets of sheer material for attaching each respective vane to the second sheet of sheer material. A shifter moves the first and second sheets of sheer material relative to one another such that the center region of the vanes are substantially parallel to the first and second sheets of sheer material. Finally, a presser presses the first sheet of sheer material, the second sheet of sheer material, and the plurality of vanes.
These and other benefits and features of the present invention will be apparent upon consideration of the following detailed description of preferred embodiments thereof, presented in connection with the following drawings in which like reference numerals identify like elements throughout.